Scope 3 Emissions and Value Chain Accounting: A Practical Guide 2026

A major customer, financier, or parent company has sent you a questionnaire asking for Scope 3 emissions data. The deadline is tight, you have no existing calculations, and your suppliers have no ready data to hand. This is the most common situation in which an SME sustainability manager begins Scope 3 accounting in 2026. This guide walks through what Scope 3 means, how value chain emissions are calculated, and how data collection works in practice.

What Scope 3 Is and Why It Matters Right Now

Scope 3 covers all other indirect greenhouse gas emissions generated in a company’s value chain. They do not arise in company-owned facilities or from purchased energy, but in suppliers’ production, in transportation, in the use of sold products, and in dozens of other categories.

Scope 1 covers a company’s own direct emissions (fuels, refrigerants, owned vehicles). Scope 2 covers emissions from purchased energy. Scope 3 is everything else. The distinction comes from the GHG Protocol Corporate Standard and is the international benchmark.

In 2026, Scope 3 is coming to the fore for three reasons. First, the CSRD directive and its ESRS standards require large companies to report value chain emissions, and those companies are asking their suppliers for data. Second, SBTi targets require Scope 3 coverage when value chain emissions are significant. Third, banks and investors want to know the value chain emissions of the companies they finance. The information cascades down the chain to SMEs.

The 15 Scope 3 Categories at a Glance

The GHG Protocol divides Scope 3 into fifteen categories. The first eight are upstream categories, relating to a company’s purchases and activities before the point of sale. The final seven are downstream categories, relating to sold products and services.

Upstream (1–8):

Purchased goods and services
Capital goods (machinery, equipment, buildings)
Fuel- and energy-related emissions not covered by Scope 1/2
Upstream transportation and distribution
Waste generated in operations
Business travel
Employee commuting
Upstream leased assets

Downstream (9–15):

Downstream transportation and distribution
Processing of sold products
Use of sold products
End-of-life treatment of sold products
Downstream leased assets
Franchises
Investments

Not all 15 categories apply to every company. Category 14 (franchises), for example, is relevant only to franchise chains. Category 15 (investments) applies primarily to financial institutions. A more detailed walkthrough is available in the article What Are Scope 3 Emissions? 15 Categories Explained.

Why Scope 3 Typically Accounts for Over 70% of Emissions

For most companies, Scope 3 makes up by far the largest share of total emissions. Based on CDP reporting data, Scope 3 is typically more than ten times greater than Scope 1+2 combined, although the distribution varies by industry.

For a service company, the largest Scope 3 source is usually Category 1 (purchased goods and services): external professional services, software, office leases, and marketing. In retail, Category 1 (goods for resale) and Category 4 (logistics) dominate. In manufacturing, raw materials (Category 1) and use of sold products (Category 11) are often the largest sources. In the building products sector, capital goods and end-of-life treatment of products stand out.

The logic is straightforward. A company itself creates only a small portion of the value, and the bulk of emissions arise before it (raw materials, manufacturing, transportation) or after it (use of the product by the customer, disposal). This is why climate targets cannot be achieved simply by changing one’s own operations.

Data Collection: Practical Challenges and How to Solve Them

The hardest part of Scope 3 accounting is data collection, not the calculation formulas. Suppliers rarely have emissions data readily available, and response rates to initial questionnaires are often low. The GHG Protocol distinguishes three ways of collecting data.

Primary data is the supplier’s own calculated emissions figure, for example a product-specific carbon footprint calculated in accordance with ISO 14067. This is the most accurate approach, but availability is limited.

Secondary data is an emissions factor drawn from general databases (e.g., Ecoinvent, DEFRA, EXIOBASE) based on industry averages or generic material coefficients. This is typically sufficient to get started.

A hybrid approach is the practical compromise, in which the largest and most material purchases are described using primary data while the remainder are covered by secondary-data coefficients. Most SME calculations start with the spend-based method (€ × sector emission factor) and gradually move to activity-based calculation for key categories. A comparison is available in the article Spend-Based vs Activity-Based: Scope 3 Calculation Methods Compared.

Building the supplier questionnaire, tracking responses, and filling data gaps takes the most time in a Scope 3 project. This is where a consultant provides clear relief: NGS sends the questionnaires, coordinates responses, and compiles the data, so your internal team does not have to manage communications with dozens of suppliers. Read more in the article Scope 3 Data Collection: How to Request Emissions Data from Suppliers.

Emissions Overlap in the Value Chain

The same tonne of emissions can appear on several companies’ Scope 3 reports. A steel mill’s Scope 1 emission is a car manufacturer’s Scope 3 Category 1, a car dealer’s Scope 3 Category 1, and a leasing company’s Scope 3 Category 8. This is not an error. The GHG Protocol is deliberately designed so that every company in the chain reports its own share of the value chain.

Overlap differs from double counting, which is an error within a single report (the same emission appearing in two categories). Overlap between companies in the value chain is a feature of the system. SBTi and other target-setting frameworks are built on this logic: every company sets its own reduction targets, and the combined global targets cover the chain once at the level of emission sources.

A more detailed treatment is available in the article Emissions Overlap: Why the Same Tonne Appears on Multiple Companies’ Reports.

SBTi Targets and Scope 3

The Science Based Targets initiative (SBTi) is the most widely used framework for validating corporate targets. Its Corporate Net-Zero Standard requires that Scope 3 targets be set when value chain emissions are significant. Under Standard V1.3, the target must cover at least 67% of total Scope 3 emissions when Scope 3 exceeds 40% of the company’s total emissions.

Version 2 is in its final stages. The second public consultation closed on 12 December 2025, and the final V2 is expected during 2026. The transition timeline is clear: targets under V1.3 remain valid until 31 December 2027, and V2 becomes mandatory for new targets from 1 January 2028. According to the draft, the Scope 3 coverage requirement will shift from the 67% threshold to a materiality-based approach: targets must be set for all categories representing at least 5% of total Scope 3 emissions. This is a draft, and details may change in the final standard.

A longer discussion is available in the article SBTi in Practice: Science-Based Climate Targets and Scope 3.

The Practical Project Path: How Scope 3 Accounting Progresses in 8–12 Weeks

A typical SME Scope 3 project progresses in four phases.

Phase 1, mapping (1–2 weeks). The company’s operations are reviewed, material Scope 3 categories are identified, and calculation boundaries are agreed. Key suppliers and data sources are identified. A rough screening calculation is carried out to pinpoint hotspots.

Phase 2, data collection (3–5 weeks). Supplier questionnaires are sent, procurement data is gathered from financial systems, along with business travel reports, waste quantities, and other required information. This is the most labour-intensive phase of the project and is where the consultant’s contribution is most concentrated.

Phase 3, calculation and review (2–3 weeks). Categories are calculated using the chosen method (spend-based, activity-based, or hybrid), emission factors are selected, and assumptions are documented. Results are reviewed with a hotspot analysis and sanity check.

Phase 4, reporting and communication (1–2 weeks). A GHG-Protocol-compliant report is compiled that can be submitted to customers, CDP, or SBTi validation. Results are reviewed with management and next steps are agreed.

The whole process typically takes 8–12 weeks when data collection starts from scratch. The verification phase (e.g., ISAE 3410 limited assurance) is a separate project undertaken afterwards.

Frequently Asked Questions

What does Scope 3 mean in practice?

Scope 3 covers all company emissions other than the company’s own direct emissions (Scope 1) and purchased energy (Scope 2). In practice, it means emissions from suppliers’ production, business travel, transportation, use of sold products, and dozens of other value chain emission sources.

Does an SME need to calculate Scope 3?

Legislation does not directly require an SME to calculate Scope 3. In practice, the requirement arrives from another direction: a major customer demands data for its CSRD report, a financier asks about climate risks, or a parent company’s SBTi target requires supplier data. This is a common situation for SMEs in 2026.

Which Scope 3 categories must be covered?

The GHG Protocol requires that all material categories be reported and that materiality be justified. Under SBTi V1.3, the target must cover 67% of Scope 3. Under the V2 draft, this shifts to a category-by-category 5% threshold. In practice, for most companies 3–6 categories account for over 90% of emissions.

How long does a Scope 3 calculation take?

A typical first Scope 3 calculation for an SME takes 8–12 weeks. Time is spent particularly on collecting supplier data and documenting assumptions. In subsequent years the work is considerably faster once the structures are in place.

What if suppliers do not provide data?

A hybrid approach is used. The primary-data questionnaire is focused on the largest and most material suppliers, and the remainder are covered with sector-specific coefficients (Exiobase, DEFRA, or equivalent). The GHG Protocol permits this, provided that the methods are documented transparently.

Is Scope 3 mandatory for SBTi?

Yes, if Scope 3 exceeds 40% of total emissions. Under V1.3, the target must cover 67% of Scope 3. Under the V2 draft, the threshold shifts to a category-by-category 5% materiality limit. For small service companies, Scope 3 is almost always above 40%, so a target is required.

Scope 3 Accounting Without the Internal Data Work

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